A 27-year-old G3P1 was referred to our department at 33 weeks of gestation with a diagnosis of fetal ovarian cyst. Previous scans were normal and didn’t reveal any other morphological anomalies.

The ultrasound examination revealed the following findings: female fetus of normal growth; stomach, kidneys, bladder and heart of normal anatomy. Placenta was of a normal appearance, the amount of amniotic fluid was increased. Abdominal circumference corresponded to 36 weeks (3 weeks larger). There was a voluminous unilocular cyst which measured 63 x 53 mm arising from the left ovary.

We excluded any signs of complications such as: ovarian torsion, hemorrhage or rupture of the cyst, visceral compression. We payed a special attention to monitoring the increased amount of the amniotic fluid which could been a result of gastrointestinal obstruction or ascites.

The subsubsequent scan performed at 36 weeks revealed the increase of the cyst size: 84 x 59 mm. Abdominal circumference corresponded to 39 weeks. There was a severe polydramnios but no other signs of complication.

Patient delivered vaginally at 37 weeks after premature rupture of membranes. The neonate was in a good condition and her delivery weight was 3500 grams.The ultrasound examination which was done after delivery confirmed the prenatal diagnosis of the left ovarian cyst. 4 days later, the girl underwent surgical aspiration of the cyst with a complete resolution of cyst.

Images 1,2: Transverse view of the abdomen, note the large intraabdominal cyst located anterior to the kidney. Image 2 shows enlarge amount of the amniotic fluid.